U.S. Pat. No. 4,297,135 to Giessen, et al. discloses alloys of iron, cobalt, nickel and chromium containing both metalloids and refractory metals. The alloys are rapidly solidified at cooling rates of 10.sup.5 -10.sup.7 .degree. C./sec. to produce an ultrafine grained metastable crystal structure having enhanced compositional homogeneity. Heat treatment converts the metastable, brittle alloys into ductile alloys with primary grains of ultrafine size which contain an ultrafine dispersion of boride as well as carbide and/or silicide particles. The powders or ribbons can be consolidated into bulk parts, and the heat treated alloys possess good mechanical properties, in particular high strength and hardness, as well as good corrosion resistance for selected compositions.
U.S. Pat. No. 4,381,943 to J. Dickson, et al. discloses a chemically homogeneous, microcrystalline powder for deposition onto a substrate. The powder is a boron containing alloy based in Fe, Ni, Co or a combination thereof.
M. Von Heimendal, et al.; in the article "The Activation Energies of Crystallization in the Amorphous Alloy METGLAS.RTM. 2826A", Journal of Materials Science, 16, (1981), pp. 2405-2410; discuss the nucleation and growth rates of the metastable phase crystals of the amorphous alloy Fe.sub.32 Ni.sub.36 Cr.sub.14 P.sub.12 B.sub.6. R. S. Tiwari, et al.; in the article, "The Effect of Tensile Stress on the Crystallization Kinetics of Metglas.RTM. 2826 Fe.sub.40 Ni.sub.40 P.sub.14 B.sub.6 ", Materials Science and Engineering, 55 (1982), pp. 1-7; discuss the influence of tensile stress on the crystallization kinetics of Metglas.RTM. 2826. The nucleation rate of the eutectic crystals was found to increase markedly with increasing stress, whereas no influence was detected on growth rate.
U.S. Pat. No. 4,439,236 to R. Ray discloses boron-containing transition metal alloys based on one or more of iron, cobalt and nickel. The alloys contain at least two metal components and are composed of ultra fine grains of a primary solid solution phase randomly interspersed with particles of complex borides. The complex borides are predominately located at the junctions of at least three grains of the primary solid-solution phase. The ultra fine grains of the primary solid solution phase can have an average diameter, measured in their longest dimension, of less than about 3 micrometers, and the complex boride particles can have an average particle size, measured in their largest dimension, of less than about 1 micrometer, as viewed on a microphotograph of an electron microscope. To make the alloys taught by Ray, a melt of the desired composition is rapidly solidified to produce ribbon, wire, filament, flake or powder having an amorphous structure. The amorphous alloy is then heated to a temperature ranging from about 0.6-0.95 of the solidus temperature (measured in .degree.C.) and above the crystallization temperature to crystallize the alloy and produce the desired microstructure. The amorphous alloy ribbon, wire, filament, flake or powder taught by Ray is consolidated under simultaneous application of pressure and heat at temperatures ranging from about 0.6-0.95 of the solidus temperature.
The following documents disclose the consolidation of amorphous alloys at a pressing temperature below the alloy crystallization temperature to produce amorphous metal compacts (which are, however, brittle) and to produce claddings:
1. U.S. Pat. No. 4,381,197 to H. Liebermann;
2. U.S. Pat. No. 4,377,622 to H. Liebermann;
3. H. Liebermann, "Warm Consolidation and Cladding of Glassy Alloy Ribbons", Mat. Sci. Eng., 46 (1980) pp. 241-248.
U.S. Pat. No. 4,503,085 to Dickson, et al. discloses amorphous alloy powders that are capable of being heated and deposited on a substrate to form a bonded, amorphous alloy layer.
Other boron-containing transition metal alloys have been conventionally cooled from the liquid to the solid crystalline state. Such alloys can form continuous networks of complex boride precipitates at the crystalline grain boundaries. These networks can decrease the strength and ductility of the alloy.
Powders of rapidly solidified, transition metal alloys have previously been processed by conventional powder metallurgy to produce compacted crystalline alloy articles. Indeed, the ability of the powders to be processed by such techniques has been one of the advantages cited for such alloys and powders. Conventional processing, however, limits the properties attainable with these alloys because it exposes the alloys to excessively high temperatures that can greatly diminish the advantages of the rapid solidification. If during conventional processing the alloy is not exposed to high temperatures, then incomplete interparticle bonding can occur, resulting in a material with low toughness and, in the extreme case, low strength. Conventional techniques have not been capable of producing the desired consolidation and bonding while retaining the fine microstructure afforded by rapid solidification. As a result, the consolidated articles do not have desired levels of hardness, strength, and toughness.